17  Unit 4: Climate Feedbacks 5E

What is causing global temperatures to rise, and why is the Arctic warming at almost 4 times the rate as the rest of the globe?

HS-ESS2-2 HS-ESS2-4 HS-ESS2-6

18 Investigative Phenomenon

18.1 🌡️ Arctic Amplification

The globe is warming, and the average temperature of the Arctic is increasing at almost 4 times the rate as the rest of the globe.

18.1.1 Driving Questions:

• If the Sun isn’t causing warming, then what is?
• What do greenhouse gases have to do with climate change?
• How are humans causing climate change?
• What is the relationship between ice sheets and warming?

19 Engage: Arctic vs Global Warming

Plot = require("@observablehq/plot")

arcticData = [
  {year: 1980, global: 0.26, arctic: 0.4},
  {year: 1985, global: 0.12, arctic: 0.3},
  {year: 1990, global: 0.45, arctic: 0.8},
  {year: 1995, global: 0.45, arctic: 0.9},
  {year: 2000, global: 0.42, arctic: 1.0},
  {year: 2005, global: 0.69, arctic: 1.5},
  {year: 2010, global: 0.72, arctic: 1.8},
  {year: 2015, global: 0.90, arctic: 2.5},
  {year: 2020, global: 1.02, arctic: 3.2},
  {year: 2024, global: 1.29, arctic: 4.1}
]

Plot.plot({
  title: "Temperature Change: Arctic vs Global Average",
  subtitle: "Anomaly relative to 1951-1980 baseline (°C)",
  width: 700,
  height: 400,
  y: {label: "Temperature Anomaly (°C)", domain: [0, 4.5]},
  x: {label: "Year"},
  color: {legend: true},
  marks: [
    Plot.line(arcticData, {x: "year", y: "arctic", stroke: "#3498db", strokeWidth: 3}),
    Plot.line(arcticData, {x: "year", y: "global", stroke: "#e74c3c", strokeWidth: 3}),
    Plot.dot(arcticData, {x: "year", y: "arctic", fill: "#3498db", r: 5}),
    Plot.dot(arcticData, {x: "year", y: "global", fill: "#e74c3c", r: 5}),
    Plot.text([{x: 2010, y: 2.3}], {x: "x", y: "y", text: d => "Arctic", fill: "#3498db", fontSize: 14, fontWeight: "bold"}),
    Plot.text([{x: 2010, y: 0.5}], {x: "x", y: "y", text: d => "Global", fill: "#e74c3c", fontSize: 14, fontWeight: "bold"})
  ]
})

19.0.1 🤔 Initial Questions

1. How much faster is the Arctic warming compared to the global average?
2. What might explain why the Arctic is warming so much faster?
3. What changes might be happening in the Arctic that could amplify warming?

20 Explore Part 1: The Greenhouse Effect

20.1 PhET Greenhouse Effect Simulation

Explore how greenhouse gases trap heat in Earth’s atmosphere:

Can't see the simulation? Open in new tab

20.1.1 🔬 Simulation Investigation Tasks

Task 1: Explore the Greenhouse Effect 1. Start with “Waves” mode to see how infrared radiation interacts with greenhouse gases 2. Compare Earth’s temperature with NO greenhouse gases vs. with greenhouse gases 3. Record the equilibrium temperature for each scenario

Task 2: Compare Different Atmospheres 1. Try the Ice Age atmosphere setting 2. Try the 1750 (pre-industrial) setting 3. Try the “Today” setting 4. Record how temperature changes with different CO₂ levels

Task 3: Photon Absorption 1. Switch to “Photons” mode 2. Observe what happens when infrared photons encounter CO₂ molecules 3. Explain why more CO₂ = more warming

20.2 CO₂ and Temperature: The Evidence

20.2.1 Ice Core Data: 800,000 Years of CO₂ and Temperature

// Ice core CO2 and temperature data
iceCoreData = [
  {kya: 800, co2: 190, temp: -8},
  {kya: 700, co2: 210, temp: -6},
  {kya: 600, co2: 240, temp: -4},
  {kya: 500, co2: 200, temp: -7},
  {kya: 400, co2: 180, temp: -9},
  {kya: 350, co2: 200, temp: -6},
  {kya: 300, co2: 240, temp: -3},
  {kya: 250, co2: 200, temp: -7},
  {kya: 200, co2: 190, temp: -8},
  {kya: 150, co2: 220, temp: -5},
  {kya: 130, co2: 280, temp: 2},
  {kya: 100, co2: 230, temp: -4},
  {kya: 50, co2: 200, temp: -6},
  {kya: 20, co2: 180, temp: -9},
  {kya: 10, co2: 260, temp: -1},
  {kya: 0.2, co2: 280, temp: 0},
  {kya: 0, co2: 420, temp: 1.2}
]

viewof showModern = Inputs.toggle({label: "Show modern CO₂ level (420 ppm)", value: false})

displayData = showModern ? iceCoreData : iceCoreData.filter(d => d.kya > 0.1)

Plot.plot({
  title: "CO₂ Concentration Over 800,000 Years",
  subtitle: "Data from Antarctic ice cores",
  width: 750,
  height: 350,
  x: {label: "Thousands of Years Ago", reverse: true, domain: [800, 0]},
  y: {label: "CO₂ (ppm)", domain: [150, showModern ? 450 : 320]},
  marks: [
    Plot.ruleY([280], {stroke: "#999", strokeDasharray: "4,4"}),
    Plot.line(displayData, {x: "kya", y: "co2", stroke: "#27ae60", strokeWidth: 2}),
    Plot.dot(displayData.filter(d => d.kya === 0), {x: "kya", y: "co2", fill: "#e74c3c", r: 10}),
    Plot.text([{x: 400, y: 295}], {x: "x", y: "y", text: d => "Pre-industrial maximum: 280 ppm", fill: "#999", fontSize: 11}),
    showModern ? Plot.text([{x: 50, y: 420}], {x: "x", y: "y", text: d => "TODAY: 420 ppm", fill: "#e74c3c", fontSize: 12, fontWeight: "bold"}) : null
  ].filter(d => d !== null)
})

20.2.2 ✅ Data Analysis

1. What is the highest CO₂ level in the past 800,000 years (before humans)?
2. What is today’s CO₂ level?
3. How does today’s CO₂ compare to the natural range?
4. What pattern do you notice between CO₂ and temperature in the ice core record?

21 Explore Part 2: The Albedo Effect

21.1 What is Albedo?

Albedo is the measure of how much light a surface reflects. It ranges from 0 (absorbs all light) to 1 (reflects all light).

albedoData = [
  {surface: "Fresh Snow", albedo: 0.85, color: "#ffffff"},
  {surface: "Sea Ice", albedo: 0.60, color: "#b3e5fc"},
  {surface: "Old Snow", albedo: 0.45, color: "#e0e0e0"},
  {surface: "Desert Sand", albedo: 0.40, color: "#fdd835"},
  {surface: "Grassland", albedo: 0.25, color: "#81c784"},
  {surface: "Forest", albedo: 0.15, color: "#2e7d32"},
  {surface: "Ocean Water", albedo: 0.06, color: "#1565c0"},
  {surface: "Asphalt", albedo: 0.04, color: "#37474f"}
]

Plot.plot({
  title: "Albedo of Different Surfaces",
  subtitle: "Higher albedo = more reflection = less heating",
  width: 700,
  height: 400,
  x: {label: "Albedo (reflection coefficient)", domain: [0, 1]},
  y: {label: "Surface Type", domain: albedoData.map(d => d.surface)},
  marks: [
    Plot.barX(albedoData, {x: "albedo", y: "surface", fill: "color", sort: {y: "-x"}}),
    Plot.text(albedoData, {x: "albedo", y: "surface", text: d => (d.albedo * 100).toFixed(0) + "%", dx: 25, fontSize: 12})
  ]
})

21.2 Interactive: Ice-Albedo Feedback Simulation

viewof iceExtent = Inputs.range([0, 100], {
  step: 5,
  value: 50,
  label: "Arctic Ice Coverage (%):"
})

avgAlbedo = (iceExtent / 100 * 0.6) + ((100 - iceExtent) / 100 * 0.06)
absorbedEnergy = ((1 - avgAlbedo) * 100).toFixed(1)
reflectedEnergy = (avgAlbedo * 100).toFixed(1)

html`
<div style="display: flex; gap: 20px; flex-wrap: wrap; margin: 20px 0;">
  <div style="flex: 1; min-width: 300px;">
    <svg width="350" height="250" style="background: linear-gradient(180deg, #87CEEB 0%, #1565c0 100%); border-radius: 10px;">
      <!-- Ice -->
      <rect x="0" y="150" width="${iceExtent * 3.5}" height="100" fill="#e3f2fd" opacity="0.9"/>
      <!-- Ocean -->
      <rect x="${iceExtent * 3.5}" y="150" width="${(100 - iceExtent) * 3.5}" height="100" fill="#0d47a1"/>
      <!-- Sun rays -->
      <line x1="175" y1="20" x2="100" y2="140" stroke="yellow" stroke-width="3" marker-end="url(#arrow)"/>
      <line x1="175" y1="20" x2="250" y2="140" stroke="yellow" stroke-width="3"/>
      <!-- Reflected rays from ice -->
      <line x1="100" y1="140" x2="50" y2="60" stroke="yellow" stroke-width="2" stroke-dasharray="5,5" opacity="${iceExtent/100}"/>
      <!-- Labels -->
      <text x="50" y="200" fill="white" font-size="12">Ice: ${iceExtent}%</text>
      <text x="250" y="200" fill="white" font-size="12">Ocean: ${100-iceExtent}%</text>
    </svg>
  </div>
  <div style="flex: 1; min-width: 250px; padding: 20px; background: #f5f5f5; border-radius: 10px;">
    <h4 style="margin-top: 0;">Energy Balance</h4>
    <p><strong>Average Albedo:</strong> ${(avgAlbedo * 100).toFixed(1)}%</p>
    <p><strong>Energy Reflected:</strong> ${reflectedEnergy}%</p>
    <p><strong>Energy Absorbed:</strong> ${absorbedEnergy}%</p>
    <div style="margin-top: 15px; padding: 10px; background: ${iceExtent < 30 ? '#ffcdd2' : iceExtent > 70 ? '#c8e6c9' : '#fff9c4'}; border-radius: 5px;">
      <strong>Effect:</strong> ${iceExtent < 30 ? '🔥 High absorption → More warming → More ice melts' : iceExtent > 70 ? '❄️ High reflection → Less warming → Ice preserved' : '⚖️ Moderate balance'}
    </div>
  </div>
</div>
`

21.3 🔬 Lab Activity: Albedo Investigation

21.3.1 Materials:

• Two identical containers with lids
• Black paper and white paper
• Two thermometers
• Heat lamp or sunny window
• Timer

21.3.2 Procedure:

1. Setup:
   • Line one container with black paper (low albedo)
   • Line the other with white paper (high albedo)
   • Place a thermometer in each container
2. Data Collection:
   • Record starting temperatures
   • Place both containers under heat lamp or in direct sunlight
   • Record temperatures every 2 minutes for 20 minutes
3. Data Table:

Time (min)	Black Container (°C)	White Container (°C)	Difference (°C)
0
2
4
6
8
10
12
14
16
18
20

4. Analysis Questions:
   • Which container heated up faster? Why?
   • How does this relate to ice-covered vs. ice-free Arctic?
   • Predict what happens as Arctic ice melts.

22 Explain: Feedback Loops in the Climate System

22.1 🔄 Understanding Climate Feedbacks

A feedback loop occurs when the output of a system affects its input, creating a cycle.

22.1.1 Positive Feedback (Amplifying)

Makes changes BIGGER - the system amplifies itself

22.1.2 Negative Feedback (Stabilizing)

Makes changes SMALLER - the system stabilizes itself

22.2 Interactive Feedback Loop Diagram

viewof feedbackType = Inputs.radio(["Ice-Albedo Feedback", "Water Vapor Feedback", "Permafrost Feedback"], {
  label: "Select feedback loop:",
  value: "Ice-Albedo Feedback"
})

feedbackInfo = {
  if (feedbackType === "Ice-Albedo Feedback") {
    return {
      steps: [
        "1. Temperature increases",
        "2. Ice and snow melt",
        "3. Darker ocean/land exposed",
        "4. More solar radiation absorbed",
        "5. Temperature increases MORE"
      ],
      color: "#3498db",
      icon: "🧊"
    }
  } else if (feedbackType === "Water Vapor Feedback") {
    return {
      steps: [
        "1. Temperature increases",
        "2. More water evaporates",
        "3. Water vapor is a greenhouse gas",
        "4. More heat trapped in atmosphere",
        "5. Temperature increases MORE"
      ],
      color: "#9b59b6",
      icon: "💨"
    }
  } else {
    return {
      steps: [
        "1. Temperature increases",
        "2. Permafrost thaws",
        "3. Trapped methane/CO₂ released",
        "4. More greenhouse gases in atmosphere",
        "5. Temperature increases MORE"
      ],
      color: "#e67e22",
      icon: "🏔️"
    }
  }
}

html`
<div style="background: linear-gradient(135deg, ${feedbackInfo.color}22, ${feedbackInfo.color}44); padding: 25px; border-radius: 15px; border-left: 5px solid ${feedbackInfo.color};">
  <h3 style="margin-top: 0;">${feedbackInfo.icon} ${feedbackType}</h3>
  <div style="display: flex; flex-direction: column; gap: 10px;">
    ${feedbackInfo.steps.map((step, i) => `
      <div style="display: flex; align-items: center; gap: 10px;">
        <div style="width: 30px; height: 30px; background: ${feedbackInfo.color}; color: white; border-radius: 50%; display: flex; align-items: center; justify-content: center; font-weight: bold;">${i+1}</div>
        <div style="flex: 1; padding: 10px; background: white; border-radius: 5px;">${step.substring(3)}</div>
        ${i < feedbackInfo.steps.length - 1 ? '<div style="font-size: 20px;">↓</div>' : '<div style="font-size: 20px;">🔄</div>'}
      </div>
    `).join('')}
  </div>
  <p style="margin-top: 15px; font-style: italic;"><strong>Type:</strong> Positive (amplifying) feedback - makes warming worse!</p>
</div>
`

22.3 🌍 Why the Arctic Warms 4x Faster

The Ice-Albedo Feedback explains Arctic amplification:

1. Arctic has lots of ice (high albedo ~60%)
2. Global warming melts some ice
3. Dark ocean exposed (low albedo ~6%)
4. Ocean absorbs 10x more energy than ice did
5. Local temperature rises dramatically
6. More ice melts → cycle continues

This is why the Arctic is the “canary in the coal mine” for climate change!

22.4 Arctic Sea Ice Decline

seaIceData = [
  {year: 1980, extent: 7.8},
  {year: 1985, extent: 7.5},
  {year: 1990, extent: 7.4},
  {year: 1995, extent: 7.1},
  {year: 2000, extent: 6.8},
  {year: 2005, extent: 6.2},
  {year: 2007, extent: 4.3},
  {year: 2010, extent: 5.0},
  {year: 2012, extent: 3.6},
  {year: 2015, extent: 4.6},
  {year: 2020, extent: 3.9},
  {year: 2024, extent: 4.2}
]

Plot.plot({
  title: "September Arctic Sea Ice Extent",
  subtitle: "Million square kilometers",
  width: 700,
  height: 400,
  x: {label: "Year"},
  y: {label: "Sea Ice Extent (million km²)", domain: [0, 9]},
  marks: [
    Plot.areaY(seaIceData, {x: "year", y: "extent", fill: "#81d4fa", fillOpacity: 0.5}),
    Plot.line(seaIceData, {x: "year", y: "extent", stroke: "#0277bd", strokeWidth: 3}),
    Plot.dot(seaIceData, {x: "year", y: "extent", fill: "#01579b", r: 5}),
    Plot.dot(seaIceData.filter(d => d.year === 2012), {x: "year", y: "extent", fill: "#e74c3c", r: 8}),
    Plot.text(seaIceData.filter(d => d.year === 2012), {x: "year", y: "extent", text: d => "Record Low: 2012", dy: -15, fill: "#e74c3c", fontSize: 11}),
    Plot.linearRegressionY(seaIceData, {x: "year", y: "extent", stroke: "#e74c3c", strokeDasharray: "5,5"})
  ]
})

22.4.1 ✅ Check Your Understanding

1. What type of feedback is the ice-albedo feedback? (positive or negative)
2. Why does exposing dark ocean water lead to more warming?
3. Calculate: If ice (albedo 0.6) is replaced by ocean (albedo 0.06), how much more energy is absorbed?
4. How does the ice-albedo feedback help explain why the Arctic warms faster than the rest of the planet?

23 Elaborate: CO₂ and Human Activity

23.1 Where Does the CO₂ Come From?

co2SourcesData = [
  {source: "Electricity & Heat", emissions: 25, color: "#e74c3c"},
  {source: "Transportation", emissions: 16, color: "#3498db"},
  {source: "Manufacturing", emissions: 21, color: "#f39c12"},
  {source: "Agriculture & Land Use", emissions: 24, color: "#27ae60"},
  {source: "Buildings", emissions: 6, color: "#9b59b6"},
  {source: "Other Energy", emissions: 8, color: "#95a5a6"}
]

Plot.plot({
  title: "Global Greenhouse Gas Emissions by Sector",
  width: 600,
  height: 400,
  x: {label: "Percentage of Global Emissions"},
  y: {label: "Sector", domain: co2SourcesData.map(d => d.source)},
  marks: [
    Plot.barX(co2SourcesData, {x: "emissions", y: "source", fill: "color", sort: {y: "-x"}}),
    Plot.text(co2SourcesData, {x: "emissions", y: "source", text: d => d.emissions + "%", dx: 20, fontSize: 12, fontWeight: "bold"})
  ]
})

23.2 CO₂ Growth Over Time

co2GrowthData = [
  {year: 1750, co2: 280, source: "Pre-industrial"},
  {year: 1800, co2: 283, source: "Historical"},
  {year: 1850, co2: 288, source: "Historical"},
  {year: 1900, co2: 296, source: "Historical"},
  {year: 1950, co2: 311, source: "Historical"},
  {year: 1960, co2: 317, source: "Mauna Loa"},
  {year: 1970, co2: 326, source: "Mauna Loa"},
  {year: 1980, co2: 339, source: "Mauna Loa"},
  {year: 1990, co2: 354, source: "Mauna Loa"},
  {year: 2000, co2: 369, source: "Mauna Loa"},
  {year: 2010, co2: 390, source: "Mauna Loa"},
  {year: 2020, co2: 414, source: "Mauna Loa"},
  {year: 2024, co2: 422, source: "Mauna Loa"}
]

Plot.plot({
  title: "Atmospheric CO₂ Concentration (1750-2024)",
  subtitle: "Parts per million (ppm)",
  width: 700,
  height: 400,
  x: {label: "Year"},
  y: {label: "CO₂ (ppm)", domain: [270, 440]},
  marks: [
    Plot.ruleY([280], {stroke: "#27ae60", strokeDasharray: "5,5"}),
    Plot.text([{x: 1800, y: 275}], {x: "x", y: "y", text: d => "Pre-industrial level: 280 ppm", fill: "#27ae60", fontSize: 10}),
    Plot.ruleY([350], {stroke: "#f39c12", strokeDasharray: "5,5"}),
    Plot.text([{x: 1800, y: 345}], {x: "x", y: "y", text: d => "\"Safe\" level: 350 ppm", fill: "#f39c12", fontSize: 10}),
    Plot.line(co2GrowthData, {x: "year", y: "co2", stroke: "#e74c3c", strokeWidth: 3}),
    Plot.dot(co2GrowthData, {x: "year", y: "co2", fill: "#c0392b", r: 4})
  ]
})

23.2.1 💡 Key Ideas: Climate Feedbacks

1. The greenhouse effect explains why increasing CO₂ leads to global warming
2. Albedo is the tendency of a surface to reflect or absorb radiation
3. Ice has high albedo (~60%) compared to seawater (~6%)
4. As ice melts, more radiation is absorbed, causing more warming → positive feedback
5. Arctic amplification (4x faster warming) is explained by ice-albedo feedback
6. Multiple feedback loops (ice-albedo, water vapor, permafrost) amplify climate change
7. Human activities have dramatically increased CO₂ levels beyond natural ranges

24 Evaluate: Modeling Climate Feedbacks

24.1 📊 Performance Task Check-In

Using what you’ve learned, you can now explain:

1. Why scientists are confident humans are causing climate change:
   • CO₂ levels are far beyond natural range (420 ppm vs. max 280 ppm)
   • The timing matches industrialization
   • Natural factors (Milankovitch cycles, solar output) can’t explain current warming
2. Why the Arctic is warming so fast:
   • Ice-albedo feedback amplifies warming
   • As ice melts, dark ocean absorbs more energy
   • This creates a self-reinforcing cycle
3. How feedbacks make climate change worse:
   • Ice-albedo: melting ice → more absorption → more melting
   • Water vapor: warming → more evaporation → more greenhouse effect
   • Permafrost: warming → methane release → more warming

24.2 Create Your Feedback Diagram

24.2.1 📝 Activity: Draw Your Own Feedback Loop

Create a diagram showing how multiple feedback loops interact:

1. Start with “Human emissions increase CO₂”
2. Show how this leads to warming
3. Include ice-albedo feedback
4. Include water vapor feedback
5. Show how they connect and amplify each other
6. Indicate which parts are observed data vs. projected consequences

Guiding Questions: - Where do humans enter this system? - Which parts of the cycle have we already observed? - What might happen if Arctic ice disappears entirely in summer? - Are there any potential negative (stabilizing) feedbacks?

---

24.3 📝 Climate Feedbacks Quiz

Question 1: What is the primary greenhouse gas that humans have increased in the atmosphere? - A) Oxygen - B) Nitrogen - C) Carbon dioxide - D) Argon

Question 2: What is albedo? - A) The amount of CO₂ in the atmosphere - B) The measure of how much light a surface reflects - C) The temperature of the ocean - D) The speed of ice melting

Question 3: Which surface has the HIGHEST albedo? - A) Fresh snow - B) Ocean water - C) Forest - D) Desert sand

Question 4: The ice-albedo feedback is an example of: - A) Negative feedback that stabilizes climate - B) Positive feedback that amplifies warming - C) No feedback effect - D) A cooling mechanism

Question 5: Why is the Arctic warming almost 4 times faster than the global average? - A) The Sun is closer to the Arctic - B) Ice-albedo feedback amplifies warming there - C) There are more people in the Arctic - D) Volcanic activity in the Arctic

Question 6: Current atmospheric CO₂ levels are approximately: - A) 280 ppm (pre-industrial level) - B) 350 ppm - C) 420 ppm - D) 1000 ppm

Question 7: In the greenhouse effect, what type of radiation do greenhouse gases absorb? - A) Visible light from the Sun - B) Ultraviolet radiation - C) Infrared radiation from Earth’s surface - D) X-rays

Question 8: The permafrost feedback involves the release of which gases? - A) Oxygen and nitrogen - B) Methane and carbon dioxide - C) Ozone and CFCs - D) Hydrogen and helium

Question 9: If Arctic sea ice (albedo 0.60) is replaced by open ocean (albedo 0.06), what happens to energy absorption? - A) Stays the same - B) Decreases slightly - C) Increases dramatically (10x more absorbed) - D) Decreases dramatically

Question 10: Which statement best explains why scientists are confident humans are causing current climate change? - A) It’s just a guess - B) Temperatures have changed before naturally - C) CO₂ levels are far beyond natural range and match timing of industrialization - D) The Sun has gotten brighter

Answers: 1-C, 2-B, 3-A, 4-B, 5-B, 6-C, 7-C, 8-B, 9-C, 10-C